U.S. patent number 6,009,580 [Application Number 08/995,183] was granted by the patent office on 2000-01-04 for method and apparatus for supporting an element to be supported, in particular the body of a patient, making it possible to support said element at a predetermined float line.
This patent grant is currently assigned to Support Systems International Industries. Invention is credited to Jean-Luc Caminade, Jean-Marc Montant.
United States Patent |
6,009,580 |
Caminade , et al. |
January 4, 2000 |
Method and apparatus for supporting an element to be supported, in
particular the body of a patient, making it possible to support
said element at a predetermined float line
Abstract
The present invention relates to a method and apparatus for
supporting a body element. The apparatus includes at least one
support device with at least one closed or controlled-release
chamber, a filling device and an emptying means device for filling
said chamber with a filling fluid and emptying the fluid from the
chamber, and a distance-measurement device for measuring the
distance between a top face and a bottom face of the chamber. The
apparatus further includes a reaction-measurement device for
measuring the reaction of the support device relative to the
morphological data of the body element to be supported, and a
control system including a combination device for combining the
measurement of the penetration distance d provided by the
distance-measurement device and the measurement of the reaction
provided by the reaction-measurement device. This combination is
advantageously constituted by summing the two obtained
measurements. The invention makes it possible to support the
element to be supported substantially in a position of equilibrium
corresponding substantially to a predetermined float line.
Inventors: |
Caminade; Jean-Luc (Saint Jean
de Vedas, FR), Montant; Jean-Marc (Montpellier,
FR) |
Assignee: |
Support Systems International
Industries (Montpellier Cedex 5, FR)
|
Family
ID: |
9498997 |
Appl.
No.: |
08/995,183 |
Filed: |
December 22, 1997 |
Foreign Application Priority Data
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Dec 23, 1996 [FR] |
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96 15848 |
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Current U.S.
Class: |
5/713; 5/710 |
Current CPC
Class: |
A61G
7/05769 (20130101); A61G 2203/34 (20130101); A61G
2203/40 (20130101) |
Current International
Class: |
A47C
27/10 (20060101); A61G 7/057 (20060101); A47C
027/10 (); A47C 031/12 (); A47C 007/057 () |
Field of
Search: |
;5/713,710,714,715,671,672 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 489 310 |
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Jun 1992 |
|
EP |
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0 676 158 |
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Oct 1995 |
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EP |
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Primary Examiner: Grosz; Alexander
Attorney, Agent or Firm: Wolf, Greenfield & Sacks,
P.C.
Claims
We claim:
1. A method of supporting an element, comprising the steps of
providing at least one support device comprising at least one
closed or controlled-release chamber that is flexible and
inflatable, said chamber having a top face and a bottom face,
providing distance-measurement means for measuring a distance
between said top face and said bottom face,
providing a reaction-measurement device for measuring a reaction of
the support device relative to morphological data of the
element,
penetrating said at least one chamber by the element,
measuring the distance between said top face and said bottom face
of said at least one chamber,
measuring the reaction of the support device to said penetration of
the element,
combining the measured reaction of the support device to said
penetration of the element with the measured distance between said
top face and said bottom face, and
bringing, based on said combining, the element substantially to a
position of equilibrium corresponding substantially to a
predetermined float line by filling or emptying said at least one
chamber with a fluid.
2. The method of claim 1, wherein said combining step includes
summing the measured distance and the measured reaction.
3. The method of claim 1, wherein said measuring step the reaction
of the support device includes measuring the pressure in said
chamber at said measured distance.
4. The method of claim 3, wherein said combining step includes
summing the measured distance and the measured pressure in the
chamber.
5. The method of claim 1, wherein said bringing step includes
comparing the combination of the measured distance and the measured
reaction with a reference value characterizing the equilibrium
value for said penetration of the element corresponding
substantially to the predetermined float line of said element.
6. The method of claim 5, wherein said bringing step includes
predetermining the reference value that defines the equilibrium
corresponding substantially to the float line by selecting a value
characteristic of optimum pressures applied to an area of the body
in contact with the support device, so as to achieve expected
performance levels as regards treating patient for or preventing
the development of in particular complications related to prolonged
periods of being confined to bed or of being kept skill, in
particular bedsores.
7. The method of claim 1, wherein said filling is performed by an
inflation device being servo-controlled to the results of the
above-mentioned combination of the measured distance and the
measured reaction of the support device.
8. The method of claim 1, wherein said step of penetrating by the
element is penetrating by a body of a patient, in particular a
patient who as undergone a skin graft, or a patient who is
suffering from skin lesions such as bedsores.
9. The method of claim 1, wherein said filling and emptying
includes inflating or deflating a multiplicity of tubes
individually, alternately and sequentially.
10. An apparatus for supporting an element, comprising
at least one support device comprising at least one closed or
controlled-release chamber that is flexible and inflatable, said
chamber having a top face and a bottom face,
filling means and emptying means for filling said chamber with a
filling fluid and emptying said fluid from said chamber,
respectively,
a distance-measurement device for measuring the distance between
said top face and said bottom face,
a reaction-measurement device for measuring a reaction of the
support device relative to morphological data of the element,
and
a control system comprising a combination device for combining the
distance measured by the distance-measurement device and the
reaction measured by the reaction-measurement device, said control
system being arranged to control said filling and emptying means so
as to bring the element substantially to a position of equilibrium
corresponding substantially to a predetermined float line.
11. The apparatus of claim 10, wherein the combination device of
the control system sums the measured distance and the measured
reaction.
12. The apparatus of claim 10, wherein the reaction-measurement
device comprises a pressure-measurement device for measuring
pressure in the chamber of the support device.
13. The apparatus of claim 10, wherein the combination device is
connected to a comparator device which compares the combination
value provided by the combination device with a reference value
provided by a reference device, the reference value characterizing
the equilibrium for penetration of the element corresponding
substantially to the predetermined float line of the element.
14. The apparatus of claim 13, wherein the element is a patient and
the reference value is set to a value characteristic of optimum
pressures applied to an area of the body of the patient in contact
with the support device for treating the patient for, or preventing
the development of, particular complications related to prolonged
periods of being confined to bed or of being kept still.
15. The apparatus of claim 10, comprising a servo-control device
for servo-controlling operation of the filling means and of the
emptying means to the result of the combination of the measured
distance and of the measured reaction.
16. The apparatus of claim 10, wherein said support device
comprises a multitude of cushions or tubes which can be deflated
individually, alternately and sequentially in the order as one of
the following every other tube, one in three tubes, or one in four
tubes, or even one in n tubes.
17. The apparatus of claim 10, wherein the element is a patient and
the support device includes a mattress for supporting the patient
who as undergone a skin graft, or the patient who is suffering from
skin lesions.
18. The apparatus of claim 10, wherein the element is a patient and
the support device includes a mattress for supporting the patient
who is suffering from bedsores.
Description
The invention relates to a method and apparatus for supporting an
element to be supported, in particular the body of a patient,
whereby the element to be supported can be supported in a position
of equilibrium essentially corresponding to a predetermined "float
line" of said element.
BACKGROUND OF THE INVENTION
Support devices are well known for supporting elements to be
supported, in particular the bodies of patients who are confined to
bed or have to be kept still for prolonged periods, in which case
such devices are generally mainly known as mattresses. It is also
well known that confining such patients to bed or keeping them
still for prolonged periods leads to complications, in particular
bedsores.
Therefore, in the prior art, various devices have been proposed for
distributing the weight of the patient over an interface body area
in contact with the support device that is as large as possible so
as to keep the interface pressures below pressures at which
capillaries become occluded, or even, in therapeutic devices, so as
to stimulate re-vascularization of tissue.
For example, Document FR-A-2 707 874 discloses a mattress designed
in particular to prevent decubitus ulcers and provides at least one
closed or controlled-release flexible chamber that is inflatable
under a pressure that is a function of the maximum penetration
distance to which the element to be supported is allowed to
penetrate into the support element, the penetration distance being
designed to be set and to be approximately in the range 12 cm to 17
cm. That prior document therefore makes provision for the filling
or emptying means to be servo-controlled so as to fill or to
deflate said chamber until the extent of penetration is brought to
approximately the set penetration distance. The penetration
distance is measured by means of a capacitive device referenced 9,
10 which can be seen clearly in FIGS. 1 and 4 of Document FR-A-2
707 874.
Furthermore, in Document FR-A-2 718 347=EP-A-676 158 the Applicant
describes a method and a system for supporting an element to be
supported, in particular the body of a patient, making it possible
to support the element at an essentially constant controlled
penetration depth by using a measurement device for measuring the
penetration distance, the measurement means differing from those of
the preceding document by the fact that they comprise a metal
element in the form of a thin film placed in the vicinity of the
top face of the support element and combined with an inductive
device forming a position detector secured to the bottom face of
the support element. Similarly, provision is made to servo-control
filling or deflating the chamber of the support element so as to
achieve the pre-set penetration distance regardless of the weight
of the element to be supported, in particular the body of a
patient.
For most patients, the prior art solutions offer a good weight/body
area ratio, i.e. they distribute well the weight of the patient
over the support device, but they suffer from the drawback of not
systematically bringing the penetration of the body of every
patient accurately to a level of natural equilibrium that procures
the ideal weight/body area distribution ratio.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, of the present invention makes it possible to support an
element to be supported, in particular the body of a patient,
essentially in a position of natural equilibrium which
substantially corresponds to a "float line" that is preferably
predefined.
The present invention also enables supporting a patient, so as to
obtain expected performance levels as regards preventing or
treating complications related to prolonged periods of being
confined to bed or of being kept still, and in particular as a
function of the morphological characteristics of the
immersed/apparent portion, in particular the weight and the body
area, and more generally the weight and the area of the element to
be supported.
The present invention also makes it possible to analyze and to
control the extent to which an element to be supported, in
particular the body of a patient, penetrates into the support
device, and the reaction that said support device exerts on the
element to be supported, in particular the body of a patient, so
that optimum pressures are applied to the body area in contact with
the support device, which is particularly desirable when preventing
and treating complications related to prolonged periods of being
confined to bed or of being kept still, in particular bedsores.
For the first time, the present invention provides a solution to
all of the above-mentioned technical problems in a manner that is
cheap, reliable and safe, easy to implement, and useable
industrially and medically.
In a first aspect, the present invention provides a method of
supporting an element to be supported, in particular the body of a
patient, said method consisting in providing at least one support
device comprising at least one closed or controlled-release chamber
that is flexible and inflatable, said chamber having a top face and
a bottom face; filling means and emptying means for filling said
chamber with a filling fluid and for emptying said fluid from said
chamber being provided together with distance-measurement means for
measuring the distance between said top face and said bottom face,
wherein a reaction-measurement device is further provided for
measuring the reaction of the support device relative to the
morphological data of the element to be supported, wherein the
penetration distance to which the element to be supported
penetrates into the support device is measured, the reaction of the
support device to penetration of the element to be supported is
measured, and the two measurements are combined so as to bring the
element to be supported substantially to a position of equilibrium
corresponding substantially to a predetermined "float line".
In an advantageous implementation of the method, the
above-mentioned combination of the measurement of the penetration
distance and of the measurement of the reaction of the support
device consists in summing the two values.
In another variant implementation, the measurement of the reaction
of the support device consists in measuring the pressure in said
chamber at said measured penetration distance.
In another variant implementation, the above-mentioned summing
consists in summing the value of the penetration distance and the
value of the pressure in the chamber.
In another variant implementation, the above-mentioned combination
of the value of the penetration distance and of the value of the
reaction measurement is compared with a reference value
characterizing the equilibrium value for penetration of the element
to be supported corresponding substantially to the predetermined
float line of said element to be supported.
In another variant implementation, the above-mentioned reference
value that is predetermined and that defines the equilibrium
corresponding substantially to the float line is set to achieve the
expected performance levels as regards treating the patient for or
preventing the development of in particular complications related
to prolonged periods of being confined to bed or of being kept
skill, in particular bedsores.
In another variant implementation, operation of the filling means
and of the emptying means is servo-controlled to the results of the
combination of the penetration distance and of the measurement of
the reaction of the support device.
In a particularly advantageous other implementation of the method
of the invention, a support device or mattress is provided that
comprises a multitude of cushions or tubes which can be deflated
individually, alternately and sequentially, in particular every
other tube, one in three tubes, or one in four tubes, or one in n
tubes, thereby avoiding relatively high pressures on various
portions of the element to be supported, in particular the body of
the patient, which are harmful to the treatment and to the comfort
of certain types of patient, in particular patients who have
undergone skin grafts or patients who suffer from acute pain
consequent upon certain diseases.
In a second aspect, the present invention also provides apparatus
for supporting an element to be supported, in particular the body
of a patient, said apparatus comprising at least one support device
comprising at least one closed or controlled-release chamber that
is flexible and inflatable, said chamber having a top face and a
bottom face, filling means and emptying means for filling said
chamber with a filling fluid and emptying said fluid from said
chamber, as well as distance-measurement means for measuring the
distance between said top face and said bottom face, said apparatus
further comprising a reaction-measurement device for measuring the
reaction of the support device relative to the morphological data
of the element to be supported, a control system comprising
combination means for combining the measurement of the penetration
distance as delivered by the distance-measurement device and the
measurement of the reaction as delivered by the
reaction-measurement device, so as to bring the element to be
supported substantially to the position of equilibrium
corresponding substantially to a predetermined "float line".
In an advantageous variant embodiment of this apparatus, the
combination device of the control system sums the penetration
distance measurement and the reaction measurement delivered by the
reaction-measurement device.
In another variant embodiment, the reaction-measurement device
comprises a pressure-measurement device for measuring the pressure
in the chamber of the support device at the measured penetration
distance.
In another variant embodiment, the combination device is connected
to a comparator device which compares the combination value
delivered by the combination device with a reference value
delivered by a reference device, the reference value characterizing
the equilibrium value for penetration of the element to be
supported corresponding substantially to the predetermined float
line of the element to be supported.
In another variant embodiment, the above-mentioned reference value
that is predetermined and that defines the equilibrium
corresponding substantially to the float line is set to achieve the
expected performance levels as regards treating the patient for or
preventing the development of in particular complications related
to prolonged periods of being confined to bed or of being kept
skill, in particular bedsores.
In another variant embodiment, said apparatus comprises a
servo-control device for servo-controlling operation of the filling
means and of the emptying means to the result of the
above-mentioned combination of the penetration distance and of the
measurement of the reaction as delivered by the measurement
device.
In an advantageous embodiment of the invention, said apparatus
comprises a support device or mattress comprising a multitude of
cushions or tubes which can be deflated individually, alternately
and sequentially, in particular every other tube, one in three
tubes, or one in four tubes, or even one in n tubes.
It can be understood that the above-mentioned method and apparatus
of the present invention solve the above-mentioned technical
problems, and, in particular, make it possible in reliable and safe
manner to support an element to be supported, preferably the body
of patient, substantially in a position of equilibrium that
corresponds substantially to a float line that is predetermined in
particular as a function of the expected performance levels as
regards prevention and therapy, and particularly as a function of
the morphological characteristics of the immersed/apparent portion,
in particular weight and body area.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, characteristics, and advantages of the invention
appear clearly on reading the following description made with
reference to two currently-preferred embodiments of the invention
given merely by way of illustration and therefore in no way
limiting the scope of the invention. It should be noted that any
characteristic that appears to be novel compared with any prior art
is claimed in its genera principle. Furthermore, FIGS. 1 to 5 are
integral parts of the present invention and therefore of the
present description.
In the figures:
FIG. 1 is a view in profile seen looking along arrow A in FIG. 2
and showing a support element which, in this example, is supporting
a patient P1 drawn in thick lines and whose morphological
characteristics are relatively larger than the morphological
characteristics of a patient P2 drawn in thin lines, both patients
P1 and P2 being shown in the supported state substantially in
equilibrium corresponding substantially to a predetermined "float
line" indicated by the dot-dash line and referenced LF;
FIG. 2 is a view similar to FIG. 1, but seen looking along arrow B
in FIG. 1;
FIG. 3 is a view of a currently-preferred embodiment of support
apparatus of the present invention, showing a patient P1 supported
substantially in equilibrium as shown in the views of FIGS. 1 and
2, and also showing the essential means of the invention making it
possible to support a patient substantially in equilibrium;
FIG. 4 shows more precisely the electronic circuit of the preferred
embodiment shown in FIG. 3 and necessary to understand the present
invention; and
FIG. 5 is a longitudinal section view showing another particular
embodiment in which the support device comprises a multitude of
independent individual inflatable tubes, it being possible to make
provision to deflate them individually and sequentially, every
other tube, one tube in three, one in four as shown, or one in
n.
MORE DETAILED DESCRIPTION
A currently-preferred embodiment of support apparatus of the
present invention is shown under the overall reference 10 in FIGS.
1 to 3. This support apparatus makes it possible to support an
element, in particular, as shown, the body of a patient P1, or the
body of some other patient P2 having different morphological
characteristics.
The apparatus 10 comprises a support device proper 11 comprising at
least one closed or controlled-release chamber 11a that is
inflatable and flexible. For example, the chamber may be made up of
a multitude of inflatable tubes that communicate with one another,
it being possible for said chamber 11a to be inflated by filling
means given overall reference 50, e.g. constituted by pump means
for pumping a filling fluid into said chamber. The chamber 11 has a
top face 12 serving to support the element to be supported P1 or
P2, and a bottom face 13 which may, for example, rest indirectly on
a base (not shown) or on equivalent means.
It can be understood that the filling means 50, such as pumping
means make it possible to fill the chamber 11a with a filling
fluid, such as a gas, in particular air, or a liquid, in particular
water. Emptying means 52 such as a valve for removing the fluid are
also provided.
The apparatus also comprises measurement means 21 for measuring the
distance d between the top face 12 of the chamber 11a and its
bottom face 13.
According to the present invention, the apparatus further comprises
a reaction measurement device 30 for measuring the reaction of the
support device 11 relative to the morphological data of the element
to be supported P1 or P2, as well as a control system comprising,
in the context of the invention, combination means 42 for combining
the penetration distance measurement delivered by the measurement
device 20 with the reaction measurement delivered by the reaction
measurement device 30.
In the context of the invention, the control system 40 comprising
the combination device 42 uses the result of the combination of the
two measurements to bring the element to be supported P1 or P2
substantially to a position of equilibrium corresponding
substantially to the predetermined float line referenced LF, by
acting on the filling means 50 or on the emptying means 52 as
defined below.
In an advantageous variant embodiment of the apparatus of the
invention, the reaction measurement device 30 comprises a
pressure-measurement device 43 for measuring the pressure p in the
chamber 11a at the measured penetration distance d.
In another advantageous variant embodiment of the apparatus of the
invention, the combination device 42 of the control system 40 sums
the penetration distance measurement d with the reaction
measurement delivered by the reaction-measurement device 30, in
particular the pressure measurement delivered by the
pressure-measurement device 43.
In a preferred embodiment of the apparatus of the invention, the
combination device 42 is connected to a comparator device 46 which
compares the combination value delivered by a combination device 42
with a reference value delivered by a reference device 45, which
reference value characterizes the equilibrium value for penetration
of the element to be supported P1 or P2 corresponding substantially
to the predetermined float line LF of the element to be supported
P1 or P2.
The comparator device 46 compares the combination value delivered
by the combination device 42 with the reference value delivered by
the reference device 45, and when the result of the comparison is
different from 0, the comparator device 46 transmits information to
a servo-control device, e.g., as in this example, comprising a
proportional-plus-integral regulation stage 47, and a control
device proper 48, and servo-controlling filling or emptying of the
chamber 11a respectively either by controlling the filling means 50
or by controlling the emptying valve 52.
It should be noted that, in the preferred embodiment shown in FIG.
3, the measurement device 20 for measuring the penetration distance
d may include a metal film 21 constrained to move with the top face
12 of the support device 11, and co-operating, in this example,
with an impedance-varying element 22, e.g. such as an induction
coil, itself co-operating, in this example, with a shielding
element 24 such as a shielding induction coil serving to guarantee
that the measurement is independent of the surrounding metal mass,
the positions of the impedance-varying element and of the shielding
element being fixed, in this example outside the chamber 11a, and
also having positions that are fixed relative to the bottom face 13
of the chamber 11a, thereby making it possible to measure the
variable distance d between the variable-position metal film 21 and
the fixed-position impedance-varying element 22.
It should be noted that, in this example, the impedance-varying
element 22 and the shielding element 24 are integral parts of a
measurement bridge 200 which is shown in detail in FIG. 4 and which
is part of an electronic circuit shown clearly in FIG. 4 and
described in detail below.
It should be noted that, naturally, when the difference between the
combination value delivered by the combination device 42 and the
reference value of the reference device 45 is zero, the point of
equilibrium has been reached which corresponds substantially to the
desired predetermined float line LF, and the servo-control system
is no longer activated.
With reference to FIG. 4, a description is given below of a
currently-preferred electronic circuit which implements the design
of the essential members as described with reference to FIG. 3.
A person skilled in the art can easily understand that the
oscillator 100 generates a sinewave signal sustained by the
transistor 1001 and whose frequency is set by the inductive
impedance of the measurement system 41 in parallel with the
capacitive impedance of the oscillator implemented by the elements
1002 & 1003.
When the metal film 21, such as an aluminum film is closest to the
impedance-varying element 22, which is a measurement induction coil
22 in this example, the measurement bridge 200 is in equilibrium.
The sinewave signal entering the bridge at points 2 and 4 is
distributed equally in the branches of the measurement bridge
because, in this example, the measurement coil 22 and the shielding
coil 24 have the same impedance. The signal between points 1 and 3
of the bridge is zero.
The further the aluminum film 21 moves away from the measurement
coil 22, the more the impedance of the measurement coil 22 differs
from the fixed impedance of the shielding coil 24, and so the
signal is distributed unequally in the branches of the bridge, and
a sinewave signal appears at terminals 1 and 3.
This sinewave signal is transformed into a DC voltage by the diode
414 and the capacitor 415 via an impedance matcher 413.
The Reference Device 45
A fixed voltage reference, which is generated by the operational
amplifier 450 serves as a reference for processing performed by the
regulation system.
The Pressure Measurement Device 43
A pressure sensor 430 disposed at an appropriate place in the
support element (a mattress in the example) and associated with a
specific power supply implemented by the element 431 delivers a DC
voltage that is proportional to the air pressure in the
mattress.
Given that the mattress is a closed casing, pressure variations are
the images of the reactions of the support to the penetration of
the patient, the electrical image of said penetration being
delivered by means of the measurement induction coil 22 integrated
in a measurement device 41 comprising the above-described
measurement bridge 200.
The elements 432, 433, and 434 amplify the signal to give it a
value that is consistent with the signal delivered by means of the
measurement device 41 having an induction coil 22 integrated in the
bridge 200.
435 is an impedance matcher.
The Aadjustment Setpoint Device 44
The adjustment setpoint device 44 gives a DC voltage that is
adjusted by means of the potentiometer 440. This adjustment is
provided to compensate for any dispersions.
The Summing Circuit 42
A summing circuit 42 implemented with an operational amplifier 420
gives an output voltage equal to the sum of the three DC voltages
processed by 41, 43, and 44. At the point of equilibrium, this sum
is equal to the reference voltage entering the differential
amplifying stage 46 described below.
The variables p and d are the inputs of a summing circuit whose
result (or output) is a constant:
p=pressure or reaction of the support, output by 43;
d=penetration distance to which the patient penetrates, output by
41; and
p+d=Cte=reference voltage. Thus, depending on the morphology of the
patient or on the position of the patient, the proportions of p
(pressure) and of d (penetration distance) are different to obtain
the constant at the regulation point.
Differential Amplifier 46
A differential amplifier 46 implemented with an operational
amplifier 460 gives an output voltage equal to twice the reference
voltage minus the output voltage of the summing circuit 42. At the
regulation point, this voltage is equal to the reference voltage.
If the system is not at its point of equilibrium, the output is
equal to the reference voltage plus or minus the voltage
proportional to the difference.
The Proportional-plus-integral Device 47
The proportional-plus-integral Device 47 serves to amplify the
difference measured at 46 while damping sudden variations in the
differences in order to avoid hunting phenomena or unwanted changes
in operating state. 471 measures the difference, and 470 is an
integrator which damps the variations in the difference. The
outputs of these two elements are applied to 472 which amplifies
the difference proportionally to its duration.
The Control Device 48 for Controlling the Filling Means or the
Emptying Means
The control device 48 comprises two window comparators which define
a low lift range 480 and a high lift range 481. The two lift ranges
overlap. The zone common to both ranges is the optimum lift zone
and corresponds to the value output from 47.
When the output from 47 decreases towards the low zone, the output
"A" from 480 changes state, and the logic system 482 causes filling
to start via the control 484 which actuates the pumping means 50.
Conversely, when the output 47 increases towards the high zone, the
output "B" of 481 changes state, and the logic system 483 causes
emptying to start via the control 485 which actuates the emptying
valve 52.
FIG. 5 shows a particularly advantageous embodiment of the
invention that is applicable in the context of an "alternating
pressure mode", with a support device or mattress comprising a
multitude of cushions or tubes 111, 112, 113, 114 to 129 which can
be individually deflated alternately and sequentially. Such
sequential deflation may be performed on every other tube, on one
in three tubes, or on one in four tubes as shown in FIG. 4, for the
tubes or cushions 114, 118, 122, 126, or even on one in five tubes
or on one in n tubes. In this context, the invention, which makes
it possible to find a support equilibrium substantially along the
float line, offers a decisive advantage by making it possible to
avoid relatively high pressures on various portions of the body
that are harmful to treatment, e.g. for skin grafts, or to comfort.
By obtaining a constant equilibrium substantially on the float
line, the invention makes it possible to maintain a pressure that
is lower than the non-vascularization pressure during the stages in
which the tissues are subjected to the pressure exerted by the
therapeutic surface during alternating operating of the type shown
in FIG. 5.
In other words, by means of the low pressures that are obtained by
the method and apparatus of the present invention, it is possible
for patients who have, for example, bedsores, regardless of whether
they have undergone skin grafts, to be treated with optimum
comfort, by putting the patient in a "floating" state in the
therapeutic surface.
* * * * *